Precise definition, diagnostic criteria, and level classification of hypertension

The latest definition of hypertension considers it a progressive cardiovascular syndrome characterized by abnormally high blood pressure, which can cause structural and functional damage to the heart, brain, kidneys, blood vessels, and other organs, ultimately leading to organ failure. This definition emphasizes that hypertension is a syndrome, not merely an elevated blood pressure reading, but an external manifestation of a systemic abnormality throughout the body. Currently, my country adopts the 2003 standards of the World Health Organization (WHO) and the International Hypertension League: ① Adults aged 18 years and older without taking antihypertensive medication have a systolic blood pressure ≥140 mmHg and/or a diastolic blood pressure ≥90 mmHg; ② Patients with a history of hypertension who are currently taking antihypertensive medication, even if their current blood pressure does not meet the above standards, are also diagnosed with hypertension. Hypertension is defined as hypertension, or essential hypertension, when two blood pressure measurements taken on different days both meet the diagnostic criteria for hypertension and the cause is unknown. The "Guidelines for the Prevention and Treatment of Hypertension in China" (2005 revised edition) uses the following definition and classification of blood pressure: Based on the level of blood pressure elevation, blood pressure is divided into grades 1, 2, and 3 (Table 1). When systolic and diastolic blood pressure belong to different grades, the higher grade is used as the standard.

Table 1. Blood Pressure Level Classification | Category | Systolic Blood Pressure (mmHg) | Diastolic Blood Pressure (mmHg) | | :--- | :--- | :--- | | Normal Blood Pressure | <120 | <80 | | High Normal | 120～139 | 80～89 | | Hypertension | ≥140 | ≥90 | | Grade 1 Hypertension (Mild) | 140～159 | 90～99 | | Grade 2 Hypertension (Moderate) | 160～179 | 100～109 | | Grade 3 Hypertension (Severe) | ≥180 | ≥110 | | Isolated Systolic Hypertension | ≥140 | ≤90 | Note: If a patient's systolic and diastolic blood pressures belong to different grades, the higher grade shall prevail. Isolated systolic hypertension can also be classified into grades 1, 2, and 3 according to systolic blood pressure levels.

Hypertension can be divided into two main categories based on its etiology: primary hypertension and secondary hypertension. Hypertension without a clear cause is called primary hypertension, also known as hypertension disease. Primary hypertension accounts for 95% of cases, and its cause is still not fully understood, but it is generally believed to be caused by a combination of factors. Secondary hypertension refers to elevated blood pressure caused by other diseases, such as chronic glomerulonephritis, renal artery stenosis, pheochromocytoma, primary aldosteronism, Cushing's syndrome, etc. Primary hypertension occurs when hypertension precedes other organ involvement; while secondary hypertension occurs when other identifiable diseases precede elevated blood pressure. Many cases of secondary hypertension, such as primary aldosteronism, pheochromocytoma, renovascular hypertension, and renin-secreting tumors, can be cured or at least improved through surgery. Therefore, it is crucial to determine whether hypertension is primary or secondary as early as possible to improve the cure rate or prevent disease progression. Hypertension is a clinical syndrome; it is not so terrible in itself, but rather the damage it causes to vital organs and physiological systems. Many organs in the human body can be damaged by hypertension. These organs are called target organs of hypertension. The main target organs of hypertension are the heart, brain, and kidneys, which can lead to serious lesions in vital organs such as the heart, brain, and kidneys, resulting in fatal or disabling diseases such as stroke, myocardial infarction, and renal insufficiency. Hypertensive cardiac damage manifests as follows: With long-term elevated blood pressure, the heart must overcome increased peripheral resistance to pump blood. Due to the compensatory effect, the myocardium becomes hypertrophic. Since the left ventricle bears the greatest pressure, the main structural change in the heart caused by hypertension is left ventricular hypertrophy, followed by dilation of the heart chambers and increased heart weight. When compensatory function is insufficient, it becomes hypertensive heart disease, and the myocardial contractility is severely weakened, leading to heart failure. Because patients with hypertension often have coronary atherosclerosis, the already burdened heart is in a state of ischemia and hypoxia, making it more prone to heart failure. Hypertensive eye diseases are classified into four grades: Grade I: Vasoconstriction and narrowing. Grade II: Arteriosclerosis, with "copper wire" or "silver wire" reactions in the arteries. Grade III: Retinal hemorrhage, exudation, and edema. Grade IV: Accompanied by optic disc edema. Retinal hemorrhage, exudation, and optic disc edema suggest damage to vital organs such as the heart, brain, and kidneys.